This invention relates to a center drive unwind system and, more particularly, to an unwind system especially advantageous in unwinding very large diameter parent rolls for subsequent rewinding into retail sized products.
Unwinds are used widely in the paper converting industry, particularly in the production of bathroom tissue and kitchen toweling. These hold parent rolls which are unwound for cross perforation and rewinding into retail-sized logs or rolls. At the time a parent roll runs out in a traditional operation, the spent shaft or core must be removed from the machine, and a new roll moved into position by various means such as an overhead crane, extended level rails, etc.
Historically, the unwinds made use of core plugs for support on unwind stands with the power for unwinding coming from belts on the parent roll surface. In contrast, center driving has been used mainly in film unwinding.
The down time associated with parent roll change represents a substantial reduction in total available run time and manpower required to change a parent roll, and hence reduces the maximum output that can be obtained from a rewinder line. The object of the invention is to dramatically reduce the time the machine is actually stopped, thus significantly improving overall efficiency, i.e., productivity while maintaining safety for all personnel.
According to the invention, the parent roll instead of being surface driven (via driven surface belts) is center driven (through the core). The invention provides an unwind stand including a pair of horizontally spaced apart side frames defining the beginning of a path of travel of the web being unwound from a parent roll for processing by a rewinder at the end of the path.
An elongated arm is pivotally mounted on each side frame with the mounting being adjacent one end of each arm and with each arm adjacent the other end being equipped with retractable chuck means for insertion into a parent roll core. Advantageously, the arms can be unitary--as part of a generally U-shaped arm means to insure stability and correspondence of operation.
Variable speed drive means are operably associated with each chuck means and are adapted to develop an increasing rotational speed characteristic in the chuck means as a parent roll carried by the chuck means is unwound. Sensor means are provided on the arms for positioning the chuck means for introduction into the core of a parent roll to be subsequently unwound.
The invention further includes the provision of a core table adjacent the frame adapted to receive from the arm means partially unwound parent roll. The core table is equipped with cradle means for rotatably supporting the partially unwound roll after the chuck means have been retracted therefrom.
Adjacent the end of the web path, i.e., adjacent the entering end of the rewinder, the invention includes means for combining the leading end portion of the web from the "new" parent roll with the trailing end portion of the substantially unwound parent roll for simultaneous introduction into the rewinder. In the illustrated embodiment, this advantageously is in the form of a thread-up conveyor utilizing vacuum.
So unlike the prior art where surface drive belts were used, there is the advantage of not contacting the surface of the parent roll when it is unwound. Other objects and advantages may be seen in the ensuing description.